1. Field of the Invention
The present invention relates to a system adapted to position an ablation catheter at a location where a pulmonary vein extends from the left atrium.
2. Description of the Related Art
Cardiac arrhythmia""s, particularly atrial fibrillation, are a pervasive problem in modem society. Although many individuals lead relatively normal lives despite persistent atrial fibrillation, the condition is associated with an increased risk of myocardial ischemia, especially during strenuous activity. Furthermore, persistent atrial fibrillation has been linked to congestive heart failure, stroke, and other thromboembolic events. Thus, atrial fibrillation is a major public health problem.
Normal cardiac rhythm is maintained by a cluster of pacemaker cells, known as the sinoatrial (xe2x80x9cSAxe2x80x9d) node, located within the wall of the right atrium. The SA node undergoes repetitive cycles of membrane depolarization and repolarization, thereby generating a continuous stream of electrical impulses, called xe2x80x9caction potentials.xe2x80x9d These action potentials orchestrate the regular contraction and relaxation of the cardiac muscle cells throughout the heart. Action potentials spread rapidly from cell to cell through both the right and left atria via gap junctions between the cardiac muscle cells. Atrial arrhythmia""s result when electrical impulses originating from sites other than the SA node are conducted through the atrial cardiac tissue.
In most cases, atrial fibrillation results from perpetually wandering reentrant wavelets, which exhibit no consistent localized region(s) of aberrant conduction. Alternatively, atrial fibrillation may be focal in nature, resulting from rapid and repetitive changes in membrane potential originating from isolated centers, or foci, within the atrial cardiac muscle tissue. These foci exhibit consistent centrifugal patterns of electrical activation, and may act as either a trigger of atrial fibrillatory paroxysmal or may even sustain the fibrillation. Recent studies have suggested that focal arrhythmia""s often originate from a tissue region along the pulmonary veins of the left atrium, and even more particularly in the superior pulmonary veins.
Several surgical approaches have been developed for the treatment of atrial fibrillation. For example, Cox, J L et al. disclose the xe2x80x9cmazexe2x80x9d procedure, in xe2x80x9cThe Surgical Treatment Of Atrial Fibrillation. I. Summaryxe2x80x9d, Thoracic and Cardiovascular Surgery 101(3):402-405 (1991) and xe2x80x9cThe Surgical Treatment Of Atrial Fibrillation. IV. Surgical Techniquexe2x80x9d, Thoracic and Cardiovascular Surgery 101(4):584-592 (1991). In general, the maze procedure is designed to relieve atrial arrhythmia by restoring effective SA node control through a prescribed pattern of incisions about the cardiac tissue wall. Although early clinical studies on the maze procedure included surgical incisions in both the right and left atrial chambers, more recent reports suggest that the maze procedure may be effective when performed only in the left atrium (see for example Sueda et al., xe2x80x9cSimple Left Atrial Procedure For Chronic Atrial Fibrillation Associated With Mitral Valve Diseasexe2x80x9d (1996)).
The left atrial maze procedure involves forming vertical incisions from the two superior pulmonary veins and terminating in the region of the mitral valve annulus, traversing the inferior pulmonary veins en route. An additional horizontal incision connects the superior ends of the two vertical incisions. Thus, the atrial wall region bordered by the pulmonary vein ostia is isolated from the other atrial tissue. In this process, the mechanical sectioning of atrial tissue eliminates the atrial arrhythmia by blocking conduction of the aberrant action potentials.
The moderate success observed with the maze procedure and other surgical segmentation procedures have validated the principle that mechanically isolating cardiac tissue may successfully prevent atrial arrhythmia""s, particularly atrial fibrillation, resulting from either perpetually wandering reentrant wavelets or focal regions of aberrant conduction. Unfortunately, the highly invasive nature of such procedures may be prohibitive in many cases. Consequently, less invasive catheter-based approaches to treat atrial fibrillation through cardiac tissue ablation have been developed.
These less invasive catheter-based therapies generally involve introducing a catheter within a cardiac chamber, such as in a percutaneous translumenal procedure, wherein an energy sink on the catheter""s distal end portion is positioned at or adjacent to the aberrant conductive tissue. Upon application of energy, the targeted tissue is ablated and rendered non-conductive.
The catheter-based methods can be subdivided into two related categories, based on the etiology of the atrial arrhythmia. First, focal arrhythmias have proven amenable to localized ablation techniques, which target the foci of aberrant electrical activity. Accordingly, devices and techniques have been disclosed which use end-electrode catheter designs for ablating focal arrhythmia""s centered in the pulmonary veins, using a point source of energy to ablate the locus of abnormal electrical activity. Such procedures typically employ incremental application of electrical energy to the tissue to form focal lesions.
The second category of catheter-based ablation methods is designed for treatment of the more common forms of atrial fibrillation, resulting from perpetually wandering reentrant wavelets. Such arrhythmias are generally not amenable to localized ablation techniques, because the excitation waves may circumnavigate a focal lesion. Thus, the second class of catheter-based approaches have generally attempted to mimic the earlier surgical segmentation techniques, such as the maze procedure, wherein continuous linear lesions are required to completely segment the atrial tissue so as to block conduction of the reentrant wave fronts.
For the purpose of comparison, ablation catheter devices and related methods have also been disclosed for the treatment of ventricular or supraventricular tachycardias, such as disclosed by Lesh, M D in xe2x80x9cInterventional Electrophysiologyxe2x80x94State Of The Art, 1993xe2x80x9d American Heart Journal, 126:686-698 (1993) and U.S. Pat. No. 5,231,995 to Desai.
While feasible catheter designs for imparting linear ablation tracks have been described, as a practical matter, most of these catheter assemblies have been difficult to position and maintain placement and contact pressure long enough and in a sufficiently precise manner in the beating heart to successfully form segmented linear lesions along a chamber wall. Indeed, many of the aforementioned methods have generally failed to produce closed transmural lesions, thus leaving the opportunity for the reentrant circuits to reappear in the gaps remaining between point or drag ablations. In addition, minimal means have been disclosed in these embodiments for steering the catheters to anatomic sites of interest such as the pulmonary veins.
None of the catheter-based ablation assemblies disclose a system adapted for positioning one end of a linear ablation element within a first ostium of a first pulmonary vein and the other end of the ablation element within a second ostium of a second pulmonary vein. Nor does the prior art disclose a method for securing the ablation element between a first and second anchor, thereby maintaining a desired linear position in contact with the atrial wall and facilitating the formation of a linear ablation track along the length of tissue between the anchors.
The present invention relates to a positioning system for guiding a catheter to a location where a pulmonary vein extends from an atrium. The system comprises a deflectable guidewire, a sheath and a catheter. The deflectable guidewire is adapted for slidable advancement through the sheath, and has a deflectable distal end so that it can be steered into a position for engagement with a pulmonary vein. The catheter is adapted for advancement over the deflectable guidewire and into the atrium.
In accordance with this mode, the deflectable guidewire comprises a wire wound coil surrounding a moveable pullwire.
In one variation of the positioning system, the deflection guidewire is integral with the catheter. The catheter preferably comprises proximal and distal ends and a moveable pullwire attached to the distal end of the catheter. The proximal end of the catheter is adapted to facilitate manipulation of the pullwire, such that manipulation of the pullwire causes deflection of the distal end of the catheter.
In a variation to the present mode, the catheter comprises an electrode element. The electrode element may be a mapping electrode, an ablation electrode, or both a mapping electrode and an ablation electrode. In one mode, the electrode element may be an RF ablation element.
Where the catheter comprises an ablation element, the ablation element may be selected from the group consisting of a microwave ablation element, a cryogenic ablation element, a thermal ablation element, a light-emitting ablation element, and an ultrasound transducer. The ablation element may be adapted to form a linear lesion, a circumferential lesion, or both.
In a variation to this mode, the guidewire may be selected from the group consisting of a guidewire, an anchor wire, and a deflectable guidewire. The anchor wire comprises an elongate body with proximal and distal end portions and having an expandable member along the distal end portion, such that radial expansion of the expandable member is adapted to anchor the guidewire within the pulmonary vein.
In accordance with another mode of the present invention, a positioning system is disclosed for guiding an ablation catheter to a location where a lumen extends from a body cavity. The positioning system comprises a deflectable guidewire and a transeptal sheath. The deflectable guidewire device is adapted to be removably engaged within the sheath, whereby the sheath and deflectable cooperate to facilitate positioning of the ablation catheter at the location when the catheter is advanced through the sheath and into the body cavity and guided toward the location.
In a variation to this mode, the deflectable guidewire is integral with the catheter, wherein the catheter further comprises proximal and distal ends and a moveable pullwire attached to the distal end of the catheter, and wherein the proximal end of the catheter is adapted to facilitate manipulation of the pullwire, such that manipulation of the pullwire causes deflection of the distal end of the catheter.
The ablation catheter comprises an ablation element, which may be selected from the group consisting of a microwave ablation element, a cryogenic ablation element, a thermal ablation element, a light-emitting ablation element, and an ultrasound transducer. The ablation element may be adapted to form a linear lesion, a circumferential lesion, or both.
In accordance with another mode of the present invention, a positioning system is disclosed for guiding an ablation catheter to a location where a pulmonary vein extends from an atrium. The system comprises a deflection device and a transeptal sheath having proximal and distal ends, wherein the deflection device is removably positionable within the transeptal sheath without extending beyond the distal end of the sheath.
In a variation to this mode of the invention, the deflection device comprises a pre-shaped stylet. In addition or in the alternative, the deflection device may comprise a pre-shaped tubular guide member.
In another variation of the positioning system, the deflection device is integral with the sheath. The sheath preferably comprises proximal and distal ends and a moveable pullwire attached to the distal end of the sheath. The proximal end of the sheath is adapted to facilitate manipulation of the pullwire, such that manipulation of the pullwire causes deflection of the distal end of the sheath.
In another variation of the positioning system, the deflection device is integral with the catheter, wherein the catheter further comprises proximal and distal ends and a moveable pullwire attached to the distal end of the catheter, and wherein the proximal end of the catheter is adapted to facilitate manipulation of the pullwire, such that manipulation of the pullwire causes deflection of the distal end of the catheter.
In another variation of the present mode, the catheter comprises an electrode element. The electrode element may be a mapping electrode, an ablation electrode, or both a mapping electrode and an ablation electrode. In one mode, the electrode element may be an RF ablation element.
Where the catheter comprises an ablation element, the ablation element may be selected from the group consisting of a microwave ablation element, a cryogenic ablation element, a thermal ablation element, a light-emitting ablation element, and an ultrasound transducer. The ablation element may be adapted to form a linear lesion, a circumferential lesion, or both.